Pdpyras

* Incorporate bugfix from `103 <https://github.com/PagerDuty/pdpyras/issues/103>`_ by av1m
* Fix the generic issue behind `102 <https://github.com/PagerDuty/pdpyras/issues/102>`_ (unsafe mix of string formatting styles)
* In HTTP retry exhaustion messages, print only the limit that got reached and not necessarily the per-status HTTP retry

Note: version 5.0.0 has been yanked; patch release v5.0.1 addresses an issue in ``setup.py``.

* **New Features:**
* Methods that assume entity wrapping like ``rget`` and ``iter_all`` now support all API endpoints
* Property ``PDSession.print_debug`` enables printing verbose log messages to ``sys.stderr``
* **Breaking Changes:**
* Removal of the deprecated method ``PDSession.set_api_key``
* End support for `Python v3.5 <https://www.python.org/downloads/release/python-350/>`_, which has reached end-of-life.
* **Deprecations:** the following will be removed in the next minor release, and use of them in v5.0.0 will trigger warnings:
* Keyword argument ``name`` of the session constructor: this previously set the name of the logger; now it has no effect.
* Keyword argument ``paginate`` of ``APISession.iter_all``: this previously could be set to ``False`` to make ``iter_all`` stop iteration after the first page of results; now it has no effect.
* Keyword argument ``attribute`` of ``APISession.iter_cursor``: this previously could be used to specify the entity wrapper name of results. The wrapper is now determined automatically and this argument has no effect.
* Function ``tokenize_url_path``
* Function (decorator) ``resource_envelope``
* Function ``object_type``
* Function ``raise_on_error``
* Function ``resource_name``
* Property ``APISession.raise_if_http_error``: this previously allowed partial results to be returned from ``iter_all`` in the case of HTTP errors; now it has no effect.
* Function ``APISession.profiler_key``

* The default value for request timeouts is now 60s.
* Method ``api_key_access`` is now implemented as a property in the class ``APISession``. Formerly it was implemented in the parent class ``PDSession`` and inherited in classes that did not need it and could not use it.
* Bug in version 4.5.1 (removed) in package distribution/build fixed

* Add a new API generator ``iter_cursor`` to :class:`APISession` that yields results from API endpoints that support cursor-based pagination, requesting the next page of results whenever needed.

* Added new error class :class:`PDHTTPError` for strictly application-level errors (i.e. HTTP responses vs. network errors), inherits from :class:`PDClientError`
* Removed unnecessary dependencies that were hold-outs from Python 2.7 compatibility (deprecated)
* Automatically add square brackets to query parameters that are of list type if the user forgets to do so, per the requirement of using `set filters <https://developer.pagerduty.com/docs/ZG9jOjExMDI5NTU2-filtering#set-filters>`_
* Fix bug: the :attr:`PDSession.stagger_cooldown` feature added in version 3.2 only applied to network error/retry; it now applies to all forms of retrial
* Add "update" keyword argument to :attr:`APISession.persist` that updates any existing resource with the provided values

* Make timeout configurable per-session as an instance variable (based on `a suggestion in pull 48 <https://github.com/PagerDuty/pdpyras/pull/48#discussion_r529711040>`_ made by badnetmask)
* Drop support for Python 2.7
* Improve code samples formatting improvement (jackton1 / `65 <https://github.com/PagerDuty/pdpyras/pull/65>`_)
* Replace deprecated escape sequence for the double-splat operator in docstrings (ashwin153 / `68 <https://github.com/PagerDuty/pdpyras/pull/68>`_)